Ignition distributor centrifugal advance mechanism

ABSTRACT

A centrifugal advance mechanism for an internal combustion engine ignition distributor. The centrifugal advance mechanism has a weight base which is directly secured to the distributor shaft. The weight base has a pair of pins which respectively pivotally support a flyweight. The flyweights have cam surfaces which engage a cam plate. The cam plate is removably secured to a pair of pins which extend through openings in the weight base and which are secured to a base plate that is connected to a pole piece of a magnetic pickup type of distributor. With this arrangement the width of the cam plate is kept at a minimum with the result that the outer contour of the cam plate can be of such a configuration as to provide a centrifugal advance mechanism where the cam has maximum rolling contact with the flyweights and minimum sliding engagement. With the arrangement described the flyweights are carried by the unsprung mass of the centrifugal advance mechanism thus reducing the moment of inertia of the sprung mass of the mechanism. The cam plate and flyweights have flat sections which become engaged at a predetermined shaft speed. This engagement serves to limit the amount of advance that can be obtained from the mechanism when the predetermined speed is attained.

United States Patent [191 Campbell et al.

[ Dec. 2, 1975 1 IGNITION DISTRIBUTOR CENTRIFUGAL ADVANCE MECHANISM [75] Inventors: Robert W. Campbell; Robert E.

Young, both of Anderson, Ind.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Jan. 23, 1974 [21] Appl. No.: 435,863

[52] US. Cl ..123/146.5 A; 64/25; 123/117 R Groom 123/1465 A Primary ExaminerCharles J. Myhre Assistant ExaminerDaniel J. OConnor Attorney, Agent, or Firm-C. R. Meland [57] ABSTRACT A centrifugal advance mechanism for an internal combustion engine ignition distributor. The centrifugal advance mechanism has a weight base which is directly secured to the distributor shaft. The weight base has a pair of pins which respectively pivotally support a flyweight. The flyweights have cam surfaces which engage a cam plate. The cam plate is removably secured to a pair of pins which extend through openings in the weight base and which are secured to a base plate that is connected to a pole piece of a magnetic pickup type of distributor. With this arrangement the width of the cam plate is kept at a minimum with the result that the outer contour of the cam plate can be of such a configuration as to provide a centrifugal advance mechanism where the cam has maximum rolling contact with the flyweights and minimum sliding engagement. With the arrangement described the flyweights are carried by the unsprung mass of the centrifugal advance mechanism thus reducing the moment of inertia of the sprung mass of the mechanism. The cam plate and flyweights have flat sections which become engaged at a predetermined shaft speed. This engagement serves to limit the amount of advance that can be obtained from the mechanism when the predetermined speed is attained.

8 Claims, 10 Drawing Figures U.S. Patent Dec. 2, 1975 Sheet 1 of 2 3,923,028

US. Patent 'Dec.2, 1975 Sheet2of2 3,923,028

IGNITION DISTRIBUTOR CENTRIFUGAL ADVANCE MECHANISM This invention relates to a centrifugal advance mechanism for internal combustion engine ignition distributors. The centrifugal advance mechanism of an internal combustion engine ignition distributor, as known to those skilled in the art, generally utilize a pair of flyweights that engage acam and as the speed of the shaft of the ignition distributor is increased the flyweights and cam operate to adjust a timing device such as a breaker cam relative to the distributor shaft. In one type of centrifugal advance mechanism, which is disclosed in the patent toI-Iartzell et al., US. Pat.'No.

2,872,537, the ignition distributor shaft is directly con-' nected to a cam. The cam cooperates with a pair of flyweights which are pivotally supported bya weight base. The weight base is rigidly connected to the breaker cam of the distributor and with the arrangement of the Hartzell et al. patent the fiyweights and weight plate are part of the sprung mass.

In another type of centrifugal advance mechanism, known to those skilled in the art, the shaft of the distributor rather than being directly' connected to the cam plate is directly connected to the weight base. In this type of distributor the flyweights are pivotally supported by the weight base and the flyweights engage a cam plate which in turn is rigidly connected to the breaker cam to adjust the breaker cam relative to the driving shaft in response to engine speed. Examples of this latter type of distributor are disclosed in the patents to Crawford et al., U.S. Pat. No. 2,107,470 and Norris et al., US. Pat. No. 2,913,543.

In the types of distributors that have been described the center portion of the cam plate has to be wide enough to accommodate a connection to 'a' cylindrical part. With the advance mechanism of the type disclosed in the I-Iartzell et al. patent the cam plate has to be large enough at its center section to accommodate a rigid connection to the driving shaft of the' ignition distributor.'With ignition distributors of the type disclosed in the Crawford et al. and Norris et al. patents the center section of the cam plate must be wide enough to make a connection with a tubular part that is connected to the breaker cam of the ignition distributor. I I p In contrast to the known centrifugal advance mechanisms described above, the centrifugal advancemechanism of this invention is arrangedsuch that the center section of the cam plate can be of a substantially smaller dimension since the center section of the cam plate is not connected directly to a cylindrical part. Since the width of the cam plate of the centrifugal advance mechanism of this invention can'be reduced it is possible to provide cam contours that result in a greater rolling action and less sliding action between the cam plate and flyweights which improves the accuracy of the mechanism.

The reduction in diameter or width of the center section of the cam plate of the centrifugal advance mechanism of this invention is achieved by connecting the cam plate directly with the timing partto be adjusted by a pair of pins which are removably connected to the cam plate and pass through slots formed in the weight plate of the centrifugal advance mechanism. With this arrangement there is no cylindrical'part forming a direct connection with the center section of the cam plate of the centrifugal advance mechanism.

It accordingly is'one of the objec'ts'of this invention to provide a centrifugal advance mechanism for an ig-' nition distributor of an internal combustion engine which has a reduced centerdim'ension and wherein increased rolling action and lessslid'i n g action between the cam plate and flyweights is achieved.-

Another object of this invention is to' provide a cen trifugal advance mechanism for an ignition distributor mass of the ignition distributor and where the center section of the camplate'is still maintained at a minimum dimension.

Still another object of this'invention is to provide 'a centrifugal advance mechanism for an ignition distributor where the cam plate can be removed from thecentrifugal advance mechanism. This object is I accomplished by connecting thecam plate to a pair of pins that are rigidly connected to'a base plate and the pole piece assembly of the distributor" by removable fastener means such as spring retainers.

Still another object of this invention is to provide a centrifugal advance mecha'nism for an ignition distribu tor which limits the centrifugal advance to a predetermined amount at a predetermined shaft speed. This is accomplished by providing'the cam and flyweights with cooperating flat sections that have substantially line contact over a predetermined length to provide a range stop or limit for the centrifugal advance mechanism when the distributor shaft'attains the limiting speed. I

A more' specific object of this invention is to provide a centrifugal advance mechanism for an internal combustion engine ignition distributor where the'shaft of the ignition distributor directly drives a weight base which pivotally supports a pairof flyweights. Disposed above the weight'base' is a cam plate which cooperates with the flyweights. The cam'plate is removablysecured to a pair of pins that pass thr'ough'slots formed in the weight base and 'which'are directly connected with the part to be adjustedby the'centrifugal advance mechanism.

IN THE DRAWINGS:

FIG. 1 is a vertical sectional view of an ignitiondistributor having a centrifugal advance mechanism made in accordance with this invention;

FIG. 2 is a top view of an ignition centrifugal advance mechanism made in accordance with this invention;

FIG. 3 is a sectional view of the mechanism shown in FIG. 2 and taken along lines 33 of FIG. 2;

FIG. 4 is a viewsimila'r to FIG. 2 but illustrating the cam plate and flyweights of the centrifugal advance mechanism in a position where further centrifugal advance is prevented due to' the configuration of the cam plate and flyweights;

FIG. 5 is a top view of the rotor of the ignition distribut'or illustrated in FIG. 1; 1

FIG. 6 is a sectional view taken along lines 66 of FIG. 5;

FIG. 7 is a plan view of a'pole piece and base plate assembly'that forms a part of the centrifugal advance mechanism shown in FIGS; 2-4;

FIG. '8 is a view of the base plate and pole piece assembly shown in FIG. 7 and looking in'the direction of arrows 8-8;

FIG. 9 is a view partly in section of the shaft and weight base assembly which provides a part of the centrifugal advance mechanism of this invention; and V FIG. is a view of the shaft and weight base assembly shown in FIG. 9 looking in the direction of arrows 10-10.

The centrifugal advance mechanism of this invention will be described for use in adjusting the pole piece or rotor of a magnetic pickup type of distributor which is used to control an electronic control system controlling the switching of a semiconductor that controls the primary winding current of an ignition coil. It is to be understood, however, that the cnetrifugal advance mechanism of this invention could be used to adjust the breaker cam of a type of distributor using breaker contacts or any other type of rotatable ignition timing part which is to be adjusted relative to a distributor shaft.

Referring now to the drawings and more particularly to FIG. 1 the reference numeral 12 designates the metallic base of an ignition distributor. The base 12 supports a distributor cap 14 formed of insulating material. The cap 14 carries a plurality of circumferentially spaced terminals 16 which, as known to those skilled in the art, are electrically connected with the spark plugs of an internal combustion engine through spark plug wires. For an eight-cylinder engine there will be eight circumferentially spaced terminals 16 carried by the distributor cap 14.

' In the type of distributor shown in FIG. 1 an ignition coil 18 for the ignition system is supported by the cap 14. It is to be understood by those skilled in the art, however, that the ignition coil could be a part separate from the ignition distributor if so desired. The ignition coil 18 is enclosed by another cap 20 which is formed of insulating material and which is secured to the top end of cap 14. The secondary winding of the ignition coil 18 is connected with a conductive insert 22 which is as fully described hereinafter engages a contact of the rotor of the ignition distributor shown in FIG 1.

The base 12 of the ignition distributor rotatably supports a shaft 23 which is driven by the camshaft of an internal combustion engine when the ignition distributor is fitted to an engine. The shaft 23 drives a pole piece or rotor 24 which has a plurality of teeth designated by reference numeral 24A illustrated best in FIGS. 7 and 8 and which is formed of magnetic material. As the rotor 24 is rotated it swings in close proximity to the inner surface of another annular pole piece 26 formed of magnetic material. The pole piece 26 has a plurality of circumferentially spaced inner teeth 26A equal in number and spacing to the teeth 24A of rotor 24. An arrangement of this type is disclosed in the patent to Falge US. Pat. No. 3,254,247. The pole piece 26 engages the top surface of an annular permanent magnet designated by reference numeral 28 having its opposite end faces magnetized with opposite magnetic polarities. The permanent magnet 28 is supported by a cup-shaped metal part 30 which also supports a magnetic pickup coil designated by reference numeral 32. The part 30 is formed of a magnetic material. The part 30 can be rotatably adjusted relative to the base 12 by movement of a pin 34 which is connected to be moved by the diaphragm of a conventional vacuum advance unit (not illustrated). The part 30 is rotatably supported on the outer surface of bearing 31 by tubular sleeve 33 which is fixed to part 30.

The permanent magnet 28 causes a flow of flux through a path that can be traced from the lower end of magnet 28, through part 30, through sleeve or retainer 33 to the lower end of rotor 24, through rotor 24, through the air gap between rotor 24 and pole piece 26 and then through pole piece 26 to the upper end of permanent magnet 28. When rotor 24 rotates the air gap between it and pole piece 26 varies due to the provision of the teeth 24A and 26A. This variation in air gap causes an alternating voltage to be induced in pickup coil 32 which is used to control the timing of an electronic ignition system. One type of such a system is disclosed in the patent to LeMasters et al., US. Pat. No. 3,605,713.

When rotor 24 is rotating the time of occurrence of the positive and negative voltage pulses of the alternating voltage induced in coil 32 can be varied (advanced) by movement of part 30 relative to base 12 or by movement of pole piece or rotor 24 relative to shaft 23. Putting it another way, a given point in the output voltage waveform of the coil 32 will be advanced relative to shaft position when rotor 24 is adjusted relative to shaft 23 by the centrifugal advance mechanism of this invention which will now be described.

Referring now more particularly to FIGS. 25 it is seen that the top end of shaft 23 is connected directly to a weight base plate designated by reference numeral 36. The weight base plate 36 has a central opening receiving the top end of the shaft and the weight base plate 36 is preferably cold staked to the top end of the shaft 23 by a circular staking operation. The weight base plate 36 carries a pair of metal spring posts 38 and 40 which are preferably cold staked into openings provided in the weight base 36. The weight base plate 36 is provided with two rectangular openings 42 and 44. In addition, the weight base plate 36 carries a pair of buttons 46 formed of a suitable plastic bearing material. The buttons have teeth (not illustrated) which are pushed into openings formed in the weight base plate 36. After the teeth are pushed through the openings they spring apart to secure the buttons to weight plate 36. The upper face of the buttons 46 provide a bearing surface of the flyweights during their swinging movement.

The pivot pins 38 and 40 pivotally support flyweights designated by reference numerals 43 and 45. To this end the flyweight 43 and 45 are provided with openings that receive the pivot pins 38 and 40 as is illustrated in FIG. 3. The lower surface of the flyweights 43 and 45 engage the bearing buttons 46 as the flyweights move relative to the weight base plate 36 when the shaft 23 is driven.

The centrifugal advance mechanism of this invention has a base plate and pole piece assembly which is generally designated by reference numeral 48. This assembly is shown in detail in FIGS. 7 and 8 and also in FIG. 3. This assembly includes a base plate designated by reference numeral 50 which carries spring posts designated by reference numerals 52 and 54. The base plate 50 has a center section and a plurality of arms extending radially therefrom designated by reference numerals 50A, 50B, 50C and 50D. The base plate 50 is secured to a bushing member 56. The bushing 56 carries and is secured to the toothed pole piece or rotor 24. The parts are preferably cold staked together but may be secured together by other means. The bushing 56 has a central opening which receives the shaft 23.

The centrifugal advance mechanism of this invention has a cam plate which is designated by reference numeral 58. The cam plate 58 has a central opening 58A which receives a part of a distributor rotor in a manner to be described hereinafter. The cam plate 58 has a pair of openings 60 which receive the posts 54 and 52 carried by the base plate 50 of the assembly 48 shown in FIG. 7. The lower surface of the cam plate 58 engages the ends of larger diameter portions 52A and 54A of the posts 52 and 54. The cam plate 58 is removably secured to the posts 52 and 54 by C-shaped spring retainers designated by reference numerals 62. The retainers 62 snap into grooves 52B and 54B formed in the posts 52 and 54. It can be seen that the cam plate 58 is rigidly connected to the base plate 50 such that the cam plate 58 and the pole piece 24 will be rotated together in the operation of the centrifugal advance mechanism of this invention. It is further seen, from FIGS. 2, 3, and 4, that the posts 52 and 54 in the final assembly of the centrifugal advance mechanism pass throughthe rectangular slots 42 and 44 formed in the weight base plate 36.

In order to provide a spring force between the cam plate 58 and the posts that pivotally support flyweights 43 and 45 a pair of springs 64 and 66 are provided. The spring 64 is connected between the top end of post 38 and the top end of post 52 while the spring 66 is connected between the top end of post 54 and the top end of post 40. As the flyweights 43 and 45 are moved outwardly under the influence of centrifugal force, the springs 64 and 66 elongate and provide the proper resistive force to provide a proper centrifugal advance in response to shaft speed.

The top end of the centrifugal advance mechanism for the ignition distributor is enclosed by a rotor generally designated by reference numeral 70 and illustrated in FIGS. 1, 5 and 6. The rotor 70 comprises a body portion designated by reference numeral 72 which is molded from a suitable insulating material. The body portion 72 carries a spring contact 74 and a conductive part 76 which overlap at their inner ends to form an electrical connection therebetween. The spring contact 74 and the conductor 76 are held to the rotor body 72 by ultrasonically welding a retainer 78 to the body 72. As seen in FIG. 1, the end of conductor 76 swings past distributor inserts 16 while spring contact 74 engages conductive insert 22.

The rotor body 72 (FIG. 6) has an internal longitudinally extending circular boss 79 which extends from an annular portion 71 and has a pair of inwardly curved sidewall portions 73 outlining ledge portions 75 each having a lower wall 77. Each ledge portion 75 has an opening which respectively receive screws 80 and 82 shown in FIG. 5. The screws 80 and 82 are screwed into the threaded openings 83 formed in the base plate 50 when rotor 70 is secured to base plate 50. One sidewall 'of the rotor body 72 has an opening or slot 85 which receives the rectangular end 50E of the arm 50A of the base plate 50.

The rotor body 72 has a pair of narrow internal rib sections 86 and 88 extending from portion 71 and another pair of internal rib sections 90 and 92 located normal to the rib sections 86 and 88 which also extend from portion 71. When the rotor 70 is secured to base plate 50, the end 50E of the arm 50A is fitted within the slot 85 formed in the rotor body 72 and the threaded openings 83 received the screws 80 and 82. The screws 80 and 82 are tightened to fasten the rotor 70 to the base plate 50. The rotor 70 has internal boss portion walls 81 which tightly engage the top side of arms 50B and 50D when the rotor is fixed to base plate 50. In adtive to the shaft. The internal lower end surfaces of ribs 86, 88, and 92 are located closely adjacent the top surface of flyweights 43 and 45 and therefore prevent any unwanted upward movement or cocking of the flyweights during operation of the mechanism. The internal end surface of annular portion 71 lies in the same plane as the ends of the ribs and aids in prevening upward movement of the flyweights over areas near the center of the cam plate.

As previously mentioned one of the advantages of the centrifugal advance mechanism of this invention is the fact that the center section of the cam plate 58 can be maintained at a relatively small width. Thus, as can be seen from FIGS. 2 and 4, the center section 58B of the cam plate 58 does not have a cylindrical part secured thereto. There is a cylindrical hole 58A in the cam plate but this hole need only be large enough in diameter to accommodate the boss 79 of the rotor body 72.

The accuracy of response of a centrifugal advance mechanism is improved if the cam plate 58 is shifted by the flyweights 43 and 45 through a rolling action rather than a sliding action. In other words, it is desired that the cam plate so engage the flyweights that the areas of contact between the parts provide a rolling action therebetween rather than a sliding action.

In order to further explain the rolling action feature of this invention let it be assumed that an imaginary straight line is drawn through the center of hole 58A in cam plate 58 and through the center of pivot post 38. The closer this imaginary line is to the point of engagement between cam plate 58 and the inner part of flyweight 43 the more the parts operate with a rolling action. Since the cam plate 58 has a minimum width, because its center section is not connected to a tubular part, the cam contour can be arranged so that contact between the camplate and flyweights is as close as possible to the above mentioned imaginary line to maximize rolling action between the parts.

The operation of the centrifugal advance mechanism of this invention will now be described. It is assumed that the centrifugal advance mechanism is installed within the base 12 of the distributor and that the shaft 23 is being driven by the internal combustion engine. As the speed of the shaft 23 increases the flyweights 43 and 45 are thrown outwardly by centrifugal force. As this happens the outer curved surfaces 58C and 58D locted at the opposite ends of the cam plate 58 engage inner walls 43A and 45A of the flyweights 43 and 45. The walls 43A and 45A are straight flat surfaces which extend along the camming finger portions 438 and 45B of the flyweights. These walls extend from a point adjacent a pivot pinhole to the end of a respective finger portion. The engagement between the cam plate 58 and the flyweights 43 and 45 causes the cam plate to be adjusted angularly relative to the shaft 23 and in a direction to advance spark timing. The inner walls 43A and 45A of the flyweights 43 and 45 and the outer contoured surface of the cam plate 58 are so designed as to provide a predetermined angular movement of cam plate 58 relative to the shaft 23 as a function of engine speed. The amount of outward movement of the flyweights 43 and 45 for a given speed is, of course, determined by the tension of springs 64 and 66.

The outer curved end surfaces of the cam plate 58, that engage the flyweights, can be designed to have different outer contours depending on the advance curve to be used with a particular internal combustion engine.

The centrifugal advance mechanism of this invention is arranged such that the contours of the flyweights 43 and 45 and the outer cam surfaces on cam plate 58 will prevent further centrifugal advance when the shaft 23 attains a predetermined speed. To this end, the cam 58 is provided with straight flat outer surfaces 58E and 58F located on opposite sides of cam 58. These surfaces merge into the curved surfaces 58C and 58C and extend to substantially the center of the cam plate. These straight flat surfaces 58E and 58F may have a length of approximately .5 inches where the total length of cam plate 58 is 2 inches. The mechanism is arranged such that the flat inner walls or surfaces 43A and 45A of flyweights 43 and 45 are in line contact with straight walls or surfaces 58E and 58F of the cam plate 58 when the shaft 23 attains a predetermined speed at which further advance is to be stopped as is illustrated in FIG. 4. Thus, when this predetermined speed is reached the straight line contact between straight sections 43A and 45A of the flyweights with flat walls 58E and 58F of the cam plate prevent any further advance of the cam plate 58 relative to the shaft 23 when the speed of the shaft 23 causes the flyweights to assume the position illustrated in FIG. 4. With the parts in the position shown in FIG. 4 the cam plate is urged in opposite directions by the flyweights but due to the straight line contact between portions of the flyweights and the straight sections of the cam plate any further movement of the cam plate 58 relative to the shaft is prevented. Thus, even if the speed of shaft 23 exceeds the predetermined range limit speed there will be no further advance in spark timing. This provides a range stop for the centrifugal advance mechanism.

It will be appreciated that as the flyweights 43 and 45 move to advance the cam plate 58 relative to the shaft 23 the pole piece or rotor 24 is also advanced relative to the shaft 23. Thus, since the cam plate 58 is directly connected (posts 52 and 54) to plate 50 which carries pole piece 24, the pole piece 24 moves with adjustment of the cam plate 58 relative to the shaft 23. This means, of course, that with a magnetic pickup type of distributor the alternating voltage induced in the pickup coil 32 is adjusted (advanced) in phase relative to the instantaneous position of the shaft 23.

The centrifugal advance mechanism of this invention has a number of advantages as compared to prior art centrifugal advance mechanisms noted herein. First of all, since the cam plate 58 is not connected at its central section with another part of the mechanism the width of the cam plate over this section can be reduced. This results as pointed out hereinbefore in providing a more accurate centrifugal advance mechanism since the mechanism operates with greater rolling action and less sliding action.

Another advantage of the centrifugal advance mechanism of this invention is the fact that the cam 58 is a part that can be removed from the centrifugal advance mechanism. Thus, in centrifugal advance mechanisms such as that disclosed in I-Iartzell et al. the shaft is brazed or otherwise secured directly to the cam plate. Where a number of these parts are stocked for later use it will be evident that both the shaft and cam plate might have to be scrapped where it is desired to provide a cam plate of a new contour for a particular type of engine. With the arrangement of this invention the cam plate 58 and the shaft 23 are separate parts.

As has been pointed out, the configuration of the flyweights 43 and 45 and the cam surfaces on cam plate 58 provide an arrangement which self-limits the advance provided by the centrifugal advance mechanism without using the normally required range stop mechanisms of previous centrifugal advance mechanisms. This provides a more accurate range limit for the centrifugal advance mechanism and also provides an arrangement which requires less parts in that the cam plate 58 and flyweights 43 and 45, because of their contours, provide the self-limiting centrifugal advance.

A further advantage of the centrifugal advance mechanism of this invention is the fact that the flyweights 43 and 45, are not a part of the sprung mass of the mechanism. Thus, the flyweights 43 and 45 are pivotally supported by the weight base plate 36 which is directly connected to the shaft. Since the flyweights are not a part of the sprung mass, the centrifugal advance mechanism of this invention is less susceptible to any inaccuracies due to inertia effects.

It will be appreciated that this centrifugal advance mechanism will be useful with distributors where the ignition coil 18 is not built into the distributor cap and where the rotor cooperates with circumferentially spaced contacts fitted into a conventional distributor cap having a conventional center electrode.

It has been pointed out herein that certain of the parts of the centrifugal advance mechanism are connected together by cold staking. These connections can be made by other methods, such as, brazing or a spinning operation.

The electronic control system, like that disclosed in the above mentioned patent to LeMasters et al., US. Pat. No. 3,605,713 may be fabricated as a module package designated by reference numeral 94 and supported by the base 12 of the distributor within distributor cap 14.

When the parts of the centrifugal advance mechanism reach the FIG. 4 position no further advance can take place as has been explained. In this position the posts 52 and 54 are not engaged with the ends of slots 42 and 44 so that these posts do not aid in providing a range stop for the mechanism.

It should be noted that the pole piece 26, permanent magnet 28 and coil winding 32 are all supported by the tubular part 30. This is accomplished by securing the pole piece 26 and permanent magnet to part 30 by screws which are not illustrated. The supporting spool 37 for coil winding 32 is clamped between the pole piece and part 30. With this arrangement the pole piece 26, the permanent magnet 28, the pickup coil 32 and the tubular support 30 all move together as a unit when adjusted by the pin 34 connected with the vacuum unit which has not been illustrated.

What is claimed is:

I. An ignition control device for an internal combustion engine comprising, a base member, a shaft rotatably supported by said base member, a weight plate secured directly to said shaft having spaced openings, a

weight plate having outer wall sections'respectively engaging said flyweights, a pair of posts rigidly connecting said cam plate and said timing control device, each of said posts extending through respective opening in said weight plate and connected respee'tively'tosaid timing control device and cam plate at points-disposed on op-' posite sides of said ,weight plate, said posts serving to maintain a predetermined axialspacin'g between cam plate and timing control device, and=a spring-connected between each pivot pin on said weight plate and each post. 1-

2. An ignition control device for an internal combustion engine comprising, a base member,ashaft adapted.

to be driven by said engine rotatably supported by said base member, a weight plate secured directly-to said shaft, a pair of pivot posts carried by saidweight plate, a flyweight pivotally supported by eaehnpivot post, an ignition timing control device located on one side of said weight plate including a vtimingflcontrol part disposed about said shaft, said control device and timing 4. Anignition distributor of the magnetic pickup type 1 comprising, a base member, a shaft rotatably supported by said base member adapted to berotatablydriven by an internal combustion engine, 'a'weight bas'es'ecured to one end of said shaft having-a pair of spaced open in'gs, pivot pins carried by said weight base, a flyweight pivoted on each pivot-pin, sai'd'flyweights' disposed above said Weight base, a base plate located below said weight base a pole piece connected'to said base plate control part being rotatably adjustable relative to said shaft, a cam plate located on an oppositesideof said weight plate and in alignment with said flyweights, said cam plate having contoured outer wall sections respectively engaging said flyweights, a pair of openings in said weight plate, a pair of posts connected to said cam plate at a point adjacent the end ofthe posts,each post extending axially through a said opening in said weight plate with an opposite end of each post connected to said timing control device whereby said cam plate and timing control device move together, and a spring connecting each weight plate pivot post with a respective post connected to said cam plate.

3. An ignition control device for developing an ignition timing control voltage for an ignition system comprising, a base member, a shaft rotatably supported by said base member, a weight plate connected directly to said shaft having a pair of openings, a pair of pivot pins carried by said weight plate, a flyweight pivotally supported by each pivot pin, an ignition timing control device located on one side of said weight plate including a laterally extending base plate and a pole piece having a plurality of teeth, said timing control device being rotatably supported by said shaft and rotatably adjustable relative to said shaft, a cam plate located on an opposite side of said weight plate having outer wall sections respectively engaging said flyweights, a pair of posts rigidly connecting said cam plate and said base plate whereby said cam plate and'timing control device rotate together, each of said posts extending through a respective opening in said weight plate and connected to said base plate and cam plate at points disposed on opposite sides of said weight plate, said posts serving to maintain a predetermined axial spacing between said cam plate and said base plate, a spring connected between each pivot pin on said weight base and each post,

and a magnetic pickup including a coil winding and a permanent magnet, said pole piece operative to cause an ignition timing voltage to be induced in said coil winding when it is rotatably driven by said shaft.

forming part of a' magnetic pickup, said pole piece disposed about said shaft and rotatably adjustable relative to'said shaft as a'function of shaft speedffirst' and secondpost' members fixed to said liase plate, lsaid'pos't members extending upwardly through said openings formed in said weight base, a cam plate disposed above said weight base connected'with said' post members whereby said cam plate and said pole piece move together and are rotatably adjustable relative to said shaft,'said'cam plate having outer contoured wall sections r'espectively engaging inner surfaces of said flyweights to adjust said cam plate andpole piece relative" to said shaft as a function of engine speed, and a spring connected respectively between each pivot pin' and each post. p I I p 5. An ignition control device for an internal'cornbustion engine having a centrifugal advance mechanism for rotatably advancing a timing control member r'elative to adrivi ng shaft as a function of shaft speed com prising, a base member, a shaft rotatably supported by said base member, a weight plate secured directly to said shaft, pivot pins carried by said weight plate, a flyweight pivotally supported by each pivot pin, a cam plate, a timing control member supported for adjust-i able movement relative to said shaft, a pair of posts rigidly connected between said cam plate and timing control member whereby they rotate together, and a spring connected between each pivot pin and each post, the amount of pivotal movement of each flyweight about its respective pivot pin being a function of shaft speed, said cam plate having curved outer surfaces located adjacent opposite ends thereof respectively engaging said flyweights and having straight outer surfaces extending inwardly from said curved surfaces toward the center of said cam plate, said straight surfaces located respectively on opposite sides of said cam plate, said flyweights having complementary straight inner surfaces, said flyweights, by pivotal movement, operative to advance said cam plate and timing control member relative to said shaft by engagement of said flyweights with said curved outer surfaces of said cam plate at speeds below a predetermined speed of rotation of said shaft, said flyweights being pivoted to positions wherein said straight inner surfaces of said flyweights engage respectively said straight outer surfaces on the opposite sides of said cam plate in line contact and over a predetermined length of contact when said shaft attains said predetermined speed, the engagement of said straight surfaces on said flyweights with said straight surfaces located on opposiste sides of said cam plate comprising means for preventing further advance of said cam plate and timing control member relative to said shaft when said shaft attains said predetermined speed.

6. A centrifugal advance mechanism for an ignition distributor for advancing a timing member relative to the driving shaft as a function of shaft speed comprising, an ignition distributor having a base member, a shaft rotatably supported by said base member, a

weight plate secured to one end of said shaft, first and second pivot pins carried by said weight plate, a flyweight pivotally supported by each pivot pin, first and second spaced openings formed in said weight plate, a cam plate, said cam plate having outer cam surfaces engaging respectively inner surfaces of said flyweights whereby said cam plate is advanced relative to said shaft by movement of said flyweights in response to shaft speed, a timing member disposed about said shaft rotatably adjustable relative to said shaft, post means rigidly connected between said cam plate and said timing member passing through said openings formed in said weight plate whereby said cam plate and timing member rotate together, a spring interposed between each post means and a respective pivot pin, and means for prevening further advance of said timing member relative to said shaft when a predetermined shaft speed is attained, said last named means comprising straight surfaces formed respectively on said cam plate and on said flyweights which become engaged in line contact when said shaft reaches said predetermined speed.

7. A centrifugal advance mechanism for adjusting a timing member of an ignition distributor relative to a driving shaft comprising, a distributor having a base, a shaft rotatably supported by said base, a timing member disposed about said shaft and rotatably adjustable relative thereto, a weight plate secured to said shaft having a pair of pivot pins secured thereto, said weight plate having a pair of openings, a flyweight pivotally supported by each pivot pin, a cam plate having outer contoured wall sections respectively engaging inner surfaces of said flyweights whereby said cam plate is rotatably adjusted relative to said shaft by movement of said flyweights, first and second posts connected to said timing member, means removably connecting said cam plate to said posts, said posts passing respectively through said openings in said weight plate, said posts connected to said cam plate and said timing member at points located on opposite sides of said weight plate whereby said cam plate and timing member are rotatably adjustable together relative to said shaft, and a spring interposed between each post and each pivot pin.

8. A centrifugal advance mechanism for advancing a magnetic hole piece relative to the driving shaft of a magnetic pickup type of distributor comprising, a distributor having a base member, a shaft rotatably supported by said base member, a bushing disposed about said shaft, a pole piece formed of magnetic material having a plurality of teeth supported by said bushing and rotatable therewith, a base plate secured to said bushing and rotatable therewith, a weight plate connected to one end of said shaft, said weight plate having first and second openings, first and second pivot pins carried by said weight plate, a flyweight pivotally supported by each pivot pin, a cam plate having an outer contour engaging inner surfaces of said flyweights to advance said cam plate relative to said shaft during movement of said flyweights, first and second post members secured to said base plate extending axially therefrom through said openings in said weight plate, said cam plate being secured to said post members, a spring connected between each post member and pivot pin, a rotor member formed of insulating material carrying an electrical contact, said rotor member secured to said base plate, a central opening in said cam plate, and an annular boss formed on the inner surface of said rotor member positioned within said opening in said cam plate, the end of said boss engaging the end of said shaft, said rotor member serving to prevent relative axial movement between parts of said centrifugal advance mechanism. 

1. An ignition control device for an internal combustion engine comprising, a base member, a shaft rotatably supported by said base member, a weight plate secured directly to said shaft having spaced openings, a pair of pivot pins carried by said weight plate, a flyweight pivotally supported by each pivot pin, an ignition timing control device located on one side of said weight plate having a timing control part disposed about said shaft, said timing control device and timing control part being rotatably adjustable relative to said shaft, a cam plate located on an opposite side of said weight plate having outer wall sections respectively engaging said flyweights, a pair of posts rigidly connecting said cam plate and said timing control device, each of said posts extending through respective opening in said weight plate and connected respectively to said timing control device and cam plate at points disposed on opposite sides of said weight plate, said posts serving to maintain a predetermined axial spacing between cam plate and timing control device, and a spring connected between each pivot pin on said weight plate and each post.
 2. An ignition control device for an internal combustion engine comprising, a base member, a shaft adapted to be driven by said engine rotatably supported by said base member, a weight plate secured directly to said shaft, a pair of pivot posts carried by said weight plate, a flyweight pivotally supported by each pivot post, an ignition timing control device located on one side of said weight plate including a timing control part disposed about said shaft, said control device and timing control part being rotatably adjustable relative to said shaft, a cam plate located on an opposite side of said weight plate and in alignment with said flyweights, said cam plate having contoured outer wall sections respectively engaging said flyweights, a pair of openings in said weight plate, a pair of posts connected to said cam plate at a point adjacent the end of the posts, each post extending axially through a said opening in said weight plate with an opposite end of each post connected to said timing control device whereby said cam plate and timing control device move together, and a spring connecting each weight plate pivot post with a respective post connected to said cam plate.
 3. An ignition controL device for developing an ignition timing control voltage for an ignition system comprising, a base member, a shaft rotatably supported by said base member, a weight plate connected directly to said shaft having a pair of openings, a pair of pivot pins carried by said weight plate, a flyweight pivotally supported by each pivot pin, an ignition timing control device located on one side of said weight plate including a laterally extending base plate and a pole piece having a plurality of teeth, said timing control device being rotatably supported by said shaft and rotatably adjustable relative to said shaft, a cam plate located on an opposite side of said weight plate having outer wall sections respectively engaging said flyweights, a pair of posts rigidly connecting said cam plate and said base plate whereby said cam plate and timing control device rotate together, each of said posts extending through a respective opening in said weight plate and connected to said base plate and cam plate at points disposed on opposite sides of said weight plate, said posts serving to maintain a predetermined axial spacing between said cam plate and said base plate, a spring connected between each pivot pin on said weight base and each post, and a magnetic pickup including a coil winding and a permanent magnet, said pole piece operative to cause an ignition timing voltage to be induced in said coil winding when it is rotatably driven by said shaft.
 4. An ignition distributor of the magnetic pickup type comprising, a base member, a shaft rotatably supported by said base member adapted to be rotatably driven by an internal combustion engine, a weight base secured to one end of said shaft having a pair of spaced openings, pivot pins carried by said weight base, a flyweight pivoted on each pivot pin, said flyweights disposed above said weight base, a base plate located below said weight base, a pole piece connected to said base plate forming part of a magnetic pickup, said pole piece disposed about said shaft and rotatably adjustable relative to said shaft as a function of shaft speed, first and second post members fixed to said base plate, said post members extending upwardly through said openings formed in said weight base, a cam plate disposed above said weight base connected with said post members whereby said cam plate and said pole piece move together and are rotatably adjustable relative to said shaft, said cam plate having outer contoured wall sections respectively engaging inner surfaces of said flyweights to adjust said cam plate and pole piece relative to said shaft as a function of engine speed, and a spring connected respectively between each pivot pin and each post.
 5. An ignition control device for an internal combustion engine having a centrifugal advance mechanism for rotatably advancing a timing control member relative to a driving shaft as a function of shaft speed comprising, a base member, a shaft rotatably supported by said base member, a weight plate secured directly to said shaft, pivot pins carried by said weight plate, a flyweight pivotally supported by each pivot pin, a cam plate, a timing control member supported for adjustable movement relative to said shaft, a pair of posts rigidly connected between said cam plate and timing control member whereby they rotate together, and a spring connected between each pivot pin and each post, the amount of pivotal movement of each flyweight about its respective pivot pin being a function of shaft speed, said cam plate having curved outer surfaces located adjacent opposite ends thereof respectively engaging said flyweights and having straight outer surfaces extending inwardly from said curved surfaces toward the center of said cam plate, said straight surfaces located respectively on opposite sides of said cam plate, said flyweights having complementary straight inner surfaces, said flyweights, by pivotal movement, operative to advance said cam plate and timing control member relative to said shaft by engagement of said flywEights with said curved outer surfaces of said cam plate at speeds below a predetermined speed of rotation of said shaft, said flyweights being pivoted to positions wherein said straight inner surfaces of said flyweights engage respectively said straight outer surfaces on the opposite sides of said cam plate in line contact and over a predetermined length of contact when said shaft attains said predetermined speed, the engagement of said straight surfaces on said flyweights with said straight surfaces located on opposiste sides of said cam plate comprising means for preventing further advance of said cam plate and timing control member relative to said shaft when said shaft attains said predetermined speed.
 6. A centrifugal advance mechanism for an ignition distributor for advancing a timing member relative to the driving shaft as a function of shaft speed comprising, an ignition distributor having a base member, a shaft rotatably supported by said base member, a weight plate secured to one end of said shaft, first and second pivot pins carried by said weight plate, a flyweight pivotally supported by each pivot pin, first and second spaced openings formed in said weight plate, a cam plate, said cam plate having outer cam surfaces engaging respectively inner surfaces of said flyweights whereby said cam plate is advanced relative to said shaft by movement of said flyweights in response to shaft speed, a timing member disposed about said shaft rotatably adjustable relative to said shaft, post means rigidly connected between said cam plate and said timing member passing through said openings formed in said weight plate whereby said cam plate and timing member rotate together, a spring interposed between each post means and a respective pivot pin, and means for prevening further advance of said timing member relative to said shaft when a predetermined shaft speed is attained, said last named means comprising straight surfaces formed respectively on said cam plate and on said flyweights which become engaged in line contact when said shaft reaches said predetermined speed.
 7. A centrifugal advance mechanism for adjusting a timing member of an ignition distributor relative to a driving shaft comprising, a distributor having a base, a shaft rotatably supported by said base, a timing member disposed about said shaft and rotatably adjustable relative thereto, a weight plate secured to said shaft having a pair of pivot pins secured thereto, said weight plate having a pair of openings, a flyweight pivotally supported by each pivot pin, a cam plate having outer contoured wall sections respectively engaging inner surfaces of said flyweights whereby said cam plate is rotatably adjusted relative to said shaft by movement of said flyweights, first and second posts connected to said timing member, means removably connecting said cam plate to said posts, said posts passing respectively through said openings in said weight plate, said posts connected to said cam plate and said timing member at points located on opposite sides of said weight plate whereby said cam plate and timing member are rotatably adjustable together relative to said shaft, and a spring interposed between each post and each pivot pin.
 8. A centrifugal advance mechanism for advancing a magnetic hole piece relative to the driving shaft of a magnetic pickup type of distributor comprising, a distributor having a base member, a shaft rotatably supported by said base member, a bushing disposed about said shaft, a pole piece formed of magnetic material having a plurality of teeth supported by said bushing and rotatable therewith, a base plate secured to said bushing and rotatable therewith, a weight plate connected to one end of said shaft, said weight plate having first and second openings, first and second pivot pins carried by said weight plate, a flyweight pivotally supported by each pivot pin, a cam plate having an outer contour engaging inner surfaces of said flyweights to advance said cam plate relative to said shaft during movement of said flyweights, first and second post members secured to said base plate extending axially therefrom through said openings in said weight plate, said cam plate being secured to said post members, a spring connected between each post member and pivot pin, a rotor member formed of insulating material carrying an electrical contact, said rotor member secured to said base plate, a central opening in said cam plate, and an annular boss formed on the inner surface of said rotor member positioned within said opening in said cam plate, the end of said boss engaging the end of said shaft, said rotor member serving to prevent relative axial movement between parts of said centrifugal advance mechanism. 